Development of brain and spinal cord in anencephalic human fetuses

Abstract

Objectives: Anencephaly is the severest form of neural tube defects. The present study was undertaken to evaluate the development of brain and spinal cord in anencephalic human fetuses (specimens). Methods: 43 specimens with anencephaly were collected after obtaining written consent from parents and clearance from ethics committee of the institute as per declaration of Helsinki guidelines. All the specimens were fixed in buffered formalin. Gross examination and histological studies of the brain and spinal cord were performed in each specimen. Results: Gestational age of fetuses varied from 18 to 40 weeks, the majority being female fetuses. 31 (72%) fetuses had only anencephaly while 9 (21%) fetuses had additional spina bifida and 3 (7%) had meningomyelocele. The brain was observed as a dark brown undifferentiated mass with complete absence of the cerebellum, pons, medulla and midbrain. In 31 fetuses (72%), the spinal cord continued rostrally into an open neural tube that connected to the undifferentiated brown mass while in 12 fetuses (28%), it merged directly into the undifferentiated brown mass. Spinal cord was normal in appearance in all fetuses with anencephaly. Spinal cord was deformed in 3 fetuses (7%) having meningomyelocele. Histological examination of brain showed venous vessels of varying caliber interspersed with connective tissue, similar to an angioma along with islets of nervous tissue which mainly comprised of scattered nerve cells, astroglial cells and cavities lined by ependyma. Conclusion: Our findings indicate that there is no functional organization of brain in anencephalic fetuses, and the survival of such fetuses is not possible. The spinal cord is normal in fetuses with anencephaly only while it is deformed in anencephalic fetuses with meningomyelocele Keywords: anencephaly; brain development; spina bifida; spinal cord development; meningomyelocele